As is very diagrammatically shown in the left-hand half of FIG. 1, in order to install booster rockets 10 laterally on the main body 20 of a launcher, user is conventionally made of two connections 21, 22, which are respectively located to the rear and to the front of each of the booster rockets. These connections must transmit to the main launcher body the static forces constituted by the thrust forces produced by the booster rockets, whilst avoiding transmitting dynamic forces corresponding to the vibrations of the booster rockets and allowing the separation and jettisoning of the latter when their action is at an end. The connections must also take account of the differential expansions occurring between the main launcher body and the booster rockets during the operation of the latter.
In practice these different functions are fulfilled by linking the rear of each of the booster rockets 10 to the main launcher body 20 by a rigid fastening device 21 e.g. incorporating a system of rods and by connecting the front of each booster rocket to the main launcher body by a ball joint attachment device 22, which takes up the thrust force.
More specifically, the front end structure 12 by which the envelope of the tank of each of the booster rockets 10 is connected to the main launcher body 20 through the front fastening device 22, comprises a cylinder 14 obliquely cut on its front face and a cone 16 extending said front face of the cylinder and terminated by a spherical cap 18. The axis of the cone 16 is e.g. inclined by approximately 12.degree. towards the main launcher body with respect to the booster rocket axis. With the exception of the spherical cap 18, the front end structure 12 is entirely of metal and also has a very complex construction. Thus, it has a single skin of varying thickness in its front part, two skins connected by stiffeners in its rear part and stiffening frames are incorporated into it to improve its rigidity.
The heavy and particularly complex character of the front structure 12 used at present is more particularly due to the fact that it must have a high rigidity in three axes due to the dynamics of the overall launcher. It must also be able to withstand the aerodynamic loads applied to it during flight and the mechanical load resulting from the transmission of the thrust force between the launcher body 20 and the booster rocket 10 across the front fastening device 22. The over dimensioning of the front end structure 22 as a result of all these considerations leads to an increase in the weight of the overall launcher, which considerably reduces the payload which the latter can carry. Moreover, any modification to the characteristics of the booster rockets makes it necessary to completely recalculate or redesign the front end structure 12.